<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>CSS基本语法</title>
    <style>
       div.box-shadow{
           width:200px;
           height: 100px;
           background-color: dodgerblue;
           box-shadow: 0 30px 0 rgba(0,0,255,0.2);
       }
    </style>
</head>
<body>
    <div class="box-shadow">
        box-shadow
    </div>
</body>

</html>